She seems to be more relaxed and foaming, so the whole area is much more wet, and I think that may be an issue.
It's a nice, smooth bit (no rough area or anything). The size is correct (it was first thing I re-checked yesterday just to be sure her head/mouth didn't grow). And as I said same bit/bridle for over a year.
BTW, I did use the bit guards in past couple times (when I used straight loose rings), and they rubbed as well as long as they became wet. Looks like she has very sensitive skin (she's white with pinky skin).
Any suggestions? I'm thinking about using vaseline on next ride to see if it helps any.